Adding a S-meter to TenTec 1254 Shortwave Receiver

This video shows how I added a relative signal-strength meter (S-meter) to the TenTec 1254 SSB, CW, AM Shortwave Receiver kit. I built this kit last year, and really enjoy it. I did a video a few months ago that showed a walk-through of its circuitry. One downside to this radio is that it does not have a S-meter, so I decided to add one.

I measured the AGC voltage vs. input signal strength, and plotted this result to better understand the voltage range I was working with. Then, I designed and built an expanded scale voltmeter that would respond to the limited voltages that the AGC circuit produces. This video shows the circuit schematic, the completed prototype, and its operation.

Category:

Science & Technology

Tags:

• W2AEW
• TenTec
• Ten-Tec
• 1254
• SSB
• CW
• AM
• shortwave
• amateur
• ham
• receiver
• kit
• signal
• strength
• meter
• s-meter
• AGC
• voltage
• expanded
• scale
• schematic
• circuit
• radio

[sb303ssb]

Great video. Where did you get the meter?

Thanks, K4DAA

[w2aew]

@sb303ssb It was in a box of parts/junk that a friend gave me a few years ago.  So, I'm sorry I can can't provide you a source.

[MEverett98]

Thanks for the great video. It was interesting how you determined how to dc bias using a graph with your measurments. I like how simple your circuit is using a dual op amp. Very handy for builders of homebrew rigs. If you where to use a S meter, would you need to have a log amp for the 6db change per S-unit?

[w2aew]

@MEverett98 Either a log amp, or an AGC circuit that responds to the log of the input power. In the case of this receiver, the AGC function is done with gain controlled amplifiers in the 2nd IF, and supplemented with PIN diode attenuation at the RF front end. The result is that the AGC vs. Power is non-linear w.r.t voltage, power or dB - so I didn't really make any attempt in this case to have any kind of calibrated response.

[spectralcodec]

Great video, thanks!



[RadioHamGuy]

Good information and video, thanks..

[orbiter8]

Great project. Thanks for the full explanation on how you got it working.

[347DIESELMOBILE]

impressive work thanks for sharing...

[royeh]

Very nice. TNX for showing this.